Ground to Ground (GTG) rockets such as the GRAD are a serious threat when hitting a territory populated by civilians. Such rockets are of relatively simple structure as they do not employ a guidance system and are devoid of an on-board controllable steering mechanism. The hitting point at the target territory is generally dependent on the distance from the launcher, the launcher's angular positioning (azimuth and inclination) and rocket's kinematics and ballistic characteristics. A variety of certain unpredictable factors may influence the accuracy of the hitting point: winds profile during the rocket flight, asymmetry of nozzle erosion during the boost phase, and missile asymmetry (geometry and center of gravity position) due to manufacturing deviations. Shortening of the boost phase and spinning of the rocket are common use techniques for improvement of rocket accuracy. Accordingly, the hitting point can be planned in advance and once the rocket is launched, its flight cannot be altered by utilization of a controllable steering mechanism.
However, the simple GTG rocket structure has a clear inherent advantage of a very simple launching means and a low-cost price tag, facilitating deployment of numerous launchers and utilization of numerous rockets which can be launched in large numbers over a long period of time towards friendly territory, which may cause not only damage to property and humans, but also substantial damage to the morale of the population which is subjected to prolonged and continuous threats.
The combined effect of kinetic energy accumulated by the impinging rocket and the detonated explosive of war-head fragments are sufficient in many cases to penetrate walls and cause significant damage to buildings. Whilst thick concrete and other structures may block penetration of the rocket, it is practically infeasible to shield buildings with armored concrete, when considering for example several cities that are in the range of a GRAD threat.
Recently a new anti-rocket system called the “IRON DOME” system (commercially available from RAFAEL, Israel) has been introduced and used by the Israel Defense Forces (IDF) for protecting various towns that are targeted by GRAD and other rockets launched from The Gaza Strip.
Basically a typical anti rocket system is based on an early warning system, unique radar that detects and tracks a flying rocket, a Battlement Control System (BMC) that estimates its flight trajectory and potential hitting area, and launches a counter missile (using inter alia on-board navigation, homing and steering systems) for intercepting the oncoming rocket. The BMC updates the interceptor trajectory using the uplink communication channel. The system must operate under very tight operational constraints including, but not limited to, determining a Predicted Interception Point (PIP) at very high accuracy and operating in an extremely short time frame, as the whole flight trajectory from launch to interception may extend, in certain operational scenarios, to only a few tens of seconds. Another significant challenge of the GTG rockets' interception relates to the lethality problem: the vulnerable area of the rocket has relatively small dimensions and is surrounded by one or two layers of steel-made balls fitted into the warhead explosive. Achievement of lethal interception is possible by using the hit-to-kill technique or by hitting of the threat's warhead by the very dense beam of relatively heavy fragments (e.g. known per se tungsten fragments of at least 35-40 grams).
So to summarize, the main challenges of GTG rocket interception are related to a very tight time budget and to a very small vulnerable area of the target's warhead.
The net effect of the specified characteristics imposes utilization of a sophisticated and costly defense system compared to a very simple and low-cost rocket launch system. Assuming, for sake of discussion, numerous launched salvos of rockets over a prolonged period of time and aimed at many different targets, this may require deployment of many IRON DOME batteries. The latter are not only susceptible to hits but also involve significant costs per each intercept, compared to the negligible costs of each launched rocket.
There is thus a need for a new counter rocket (or possibly other flying object) system.